The Meiyu Front (Plum Rains-East Asia Monsoon).
- Meiyu Front intro.
- MCC/MCS/Durations/Regions.
- Front movement/ENSO.
- Monsoonal pattern/Convection.
- Multicell.
Plum rains coinciding with the east asia spring summer arrival of the prized sweet fleshy fruit with rains from the meiyu front thought to drive plums right of the branch straight into the plum sauce.
Meiyu Front Intro.
The Meiyu Front (Plum Rains) forms in spring-summer in East Asia and is caused by the frontal formation of weather that seperates Northern Cooler Air (Mongolian-Tibet Band) from Warmer Southern tropical air masses (Phillipinnes Band).
The creation of this front coincides with Spring-Summer in East Asia and the quasi stationary front stretches from the Tibetan Plateau north east to near the Yellow seas and North East Asia when the system is in the North Front Position.
Along this weather boundary can be found Occasional Heavy Downpours, Rain, Convection systems, Hail at times, Tornado production, and localised gust front winds. The Meiyu front can be determined therefore to sometimes bring:
- Derechos.
- Multi-Cell storms.
- Sometimes severe storms (Strong El-Nino years around the spring-summer months).
MCC-MCS/Durations/Movement/Regions.
Two types of Thunderstorm families usually develop along the stationary front the MCS convective family that then contains the MCC a sub family of convective storms.
- MCS:Mesocyclone Convective System.
- MCC:Mesoscale Convective Complex.
The formation of the storm front can resemble a linear (squall line) shape or cylindrical shape of thunderstorms or a MCC in individualised areas yet as part of one singular cohesive region along the Meiyu front.
The formation of the Meiyu front is therefore prominent from afternoon-evening-early hour mornings in East Asia due to the MCS-MCC storm family type and the event may last from 5 to 12 hours in duration and can cover up to four to six provinces but storms typically will be sporadic in nature as they cycle through there lifespan.
The spring to summer range of the Meiyu front duration and effects can last from a few days duration up 21+ days in effect.
Therefore the Meiyu Front can be scientifically termed a storm engine that can sustain momentum and energy over hours at a time when the front is present.
Spatially the Meiyu front affects East Asia regions
- South China.
- Taiwan.
- The Yanghtze river regions.
- Main Islands of the central West Pacific.
- Korea.
The movement of the Front is moving position from the stationary front south of East Asia (Southern China to Taiwan/East China) then moving slightly North to the Yangtze River/Japan/Korea areas. The Meiyu front is closely linked to the EAT in spring and summer.
Monsoonal Pattern/Convection fronts/Multicell structure.
Studies indicate that the Meiyu front is influenced by ENSO with Hot El-Nino years strengthening the front leading to stronger convection and rainfall whilst opposite La-Nina years weaken the Meiyu Front.
We have conducted a study and can confirm in the 2016 El-Nino year in east asia that the Meiyu front produced more rain in the southern section of East Asia over the 3 summer months from May to Aug 2016 then in the 2020 La- Nina years for the same area. The central east Asia area of the rainfall in 2016 (El-Nino) and 2020 (La-Nina) years are near identical with 2020 having slightly more rainfall near the Yangtze River span.
The EAT and Meiyu front are linked to the east asian spring into summer tropical monsoon pattern where humidity/moisture/warm air rising and low surface pressure play a part in the type and severity of rain-fall/convection produced by the front in the East Asian spring-summer time span. This monsoon pattern is also linked with the Tibetan/Mongolia cold air mass to create the Meiyu Front.
Different pronunciations for the Spring and Summer East Asia Front.
- China - Meiyu.
- Japan - Baiu.
- Korea - Changma.
Tropical Monsoonal spring-summer conditions and Stationary fronts from the EAT assist highly in the dynamic unfolding of this weather front in East Asia also helped by the fact that the Tibetan Plateau is at 14,800 feet above sea level.
This naturally lowers the air pressure here and cools air that is infed to the front lower atmosphere from Tibet. As this air jet moves into south Asia the Cold Tibet air meets warmed moist air molecules from south east asia with moisture infeed from the Bay of Bengal/South China seas.
From here the two circumstances of Wind Shear along with CAPE/MUCAPE/SBCAPE will create the necessary ingredients to trigger convection along the front in spring-summer within areas of East Asia.
Areas affected by the front at times are best prepared for Flooding in lowlands and water up to the window sill of cars or in excess off maximum.
Heavy winds and mudslides are also a consideration as can be hail and wind damage on the Meiyu fronts appearance especially in Strong El-Nino years.
Heavy rain output from the Meiyu Front are thought to derive from strong updrafts that carry the warmed monsoonal air parcels of moisture high into the storm. Then these cool rapidly to produce large rain droplets that then output intense bursts of rainfall as the air can no longer hold the droplets afloat. On another rain scale droplets can be smaller within weaker updrafts that will then produce a region of continual rains at a weaker hourly output aka drizzle or rain sheets.
Multicellular Front.
End on view from the south of the Meiyu Front as a MCC.
Above is the probable end view from the south of the typical layout of the Meiyu front . At this early stage of the front the typical layout of this system will evolve and change over time as is typical of all multicell storms. As lead cells in the front are created other cells will also follow and then a system of Squall Line storms begin that sometimes long lived convective systems (Hours at a time) called Derechos.
The progress system of the multicell front is trigger - developing - matured - dissipation and takes hours to complete usually in the afternoon/evening/early morning hours.